Manually operated dispensing pumps for liquid containers have been proposed in the past, and one having wide commerical application is disclosed in U.S. Pat. No. 3,749,290 issued to Micallef on July 31, 1973. This patent disclosed a variable volume pump chamber formed by a flexible tubular member, the volume of the chamber being varied by the trigger distorting the tube. Another dispensing pump is disclosed in U.S. Pat. No. 3,973,700 issued to Schmidt et al on Aug. 10, 1976. This patent shows the use of a resilient bellows as the variable volume pump chamber, with all the valving molded integrally with the bellows structure.
The use of a tubular member as shown by Micallef calls for a very flexible and resilient material such as rubber which may not be chemically resistant to many of the liquids intended to be dispensed. The use of a bellows overcomes this problem of freedom of material selection, however valving flaps in a bellows structure such as dicclosed by Schmidt et al provides for only minimal pressure to be exerted on the sealing surfaces of the flaps, thereby making it difficult to achieve a liquid tight seal.
In both pump types referred to above it is possible for vapors to be generated by the liquid in the container, i.e. under conditions of exposure to heat, such action can force liquid from the bottle into the pump chamber and through the discharge valve out into the open. This is in part due to the fact that the discharge valves are resilient and yield even to small pressures. For the same reason, both pump types referred to have the drawback that the spray pattern and liquid dispersion depends on the speed with which the trigger is pressed; a slow trigger movement resulting in a wet spray with large droplets or a stream, even when a fine, evenly dispersed spray pattern may be desired. Furthermore, these types of pumps are expensive, requiring parts of complex structure which are relatively costly to both manufacture and assemble.
Attempts to more evely regulate product flow by regulation of the amount of container available for collapse, i.e. reduced volume, have included the use of bellows for such purpose as indicated by U.S. Pat. No. 3,255,933 to Martin. U.S. Pat. No. 3,409,184 to Stengle, Jr. additionally utilized an axially collapsible bellows to receive product prior to dispensing such by its collapsing action.
Other prior art known to the applicant includes U.S. Pat. Nos. 3,061,202; 3,451,597; 3,486,663; 3,715,060; 3,726,442, 3,905,520, 3,986,644 and 3,955,774.
The above indicated patents are those which applicant is aware of and their citation herein and discussion where believed appropriate constitutes applicant's Prior Art Statement. A copy of each such patent is included with the application at the time of filing thereof.